1. The Field of the Invention
The present invention relates generally to a method and apparatus for positioning, skewing (or orienting) and feeding at least two boards into one or more saws simultaneously as part of a sawing operation. More particularly, the present invention relates to a method and apparatus in which the at least two boards are separately positioned and oriented, and feed into the one or more saws.
2. The Background Art
The demand for lumber has increased do an increase in residential and commercial building activity which utilizes lumber. In addition, wood has traditionally been in demand for furniture and other finished products. Furthermore, environmental regulation has limited the supply of raw timber. As a result, the amount of trees suitable for producing lumber is decreasing and the cost of lumber is increasing. Thus, the timber industry continually searches for ways to optimize lumber production by increasing (1) the yield rate, and (2) the piece rate. For example, it is desirable to maximize the amount of usable lumber from a single piece of raw wood. As another example, it is desirable to increase the production rate and efficiency of lumber production. Thus, two goals of lumber production are (1) accuracy in cutting the lumber to maximize yield, and (2) speed and efficiency in cutting the lumber to maximize the production or piece rate.
Sawmills typically utilize a number of machines to reduce raw trees to usable lumber. Such machines include headrig machines which cut opposite edges of the initial rounded log; ganged saws which cut the wood into a number of flat or mostly flat boards; edger machines which cut rounded sides off the flat boards; trimmer machines which cut the boards to length, etc. The machines are usually arranged so that the wood follows a path through the various machines, or flows through the sawmill.
It will be appreciated that raw wood or trees are often irregular and contain imperfections. For example, a piece of wood may be crooked or bent; have indentations or areas of reduced diameter; and have splits or other voids. Thus, a system which treats all pieces the same will inevitably produce a great deal of lumber which is unusable due to the irregularities and imperfections, and thus is wasted.
Some machines allow an operator to position and/or orient the wood in an attempt to maximize the usable lumber and avoid imperfections. For example, an operator may position a board with respect to an edger saw so that the board is fed into the edger saw with respect to particular saw blades to maximize the yield. The saw blades are usually spaced at specific and different increments so that a particular board may be cut in multiple ways. The position of the board with respect to the blades determines the size and number of cuts. Thus, the operator may take note of any irregularities or imperfections in the board and position the board with respect to the saw blades to maximize the usable lumber. In addition, some machines allow the operator to skew or pivot the board with respect to the feed axis of the saw. Thus, the board may not only be positioned with respect to particular saw blades, but also may be aligned or oriented with the feed axis to maximize the yield. One such machine allows the operator to grasp the board with the machine at a distant staging area and skew the board with respect to a reference line which is parallel with, and distant from, the feed axis. The operator may then independently transport the properly skewed board to a feed area and position the board with respect to the blades, while the board remains properly skewed.
Various machines or parts of the process may be automated or partially automated. It is desirable to automate the process as much as possible to remove any operator error. For example, an operator may position or orient a board based on the best judgement of the operator because it is not economically or physically feasible for the operator to stop the process and measure every board to determine the maximum possible yield.
As indicated above, it is also desirable to optimize the process for speed, as well as efficiency. Such optimization includes the manner in which the wood is handled. For example, many machines are designed to process a single board at a time. Thus, other associated equipment is similarly designed to process a single board at a time. Although the equipment runs continuously, standard piece rates are approximately 30-35 pieces per minute for a computer operated system, while manual systems run at a maximum of 15 pieces per minute.
Some effort has been directed towards increasing the piece rate by more rapidly handling the wood. For example, U.S. Pat. No. 5,115,846, issued May 26, 1992, to Miller et al., discloses an edger charger system with a positive-action, pinch-roll mechanism moved under the influence of a linear positioner which rapidly shuttles a board from a precharge station to an intake station. The system of Miller et al. allegedly achieves piece rates of 45 pieces per minute.
One disadvantage with such equipment is that they are designed to process a single board at a time. As indicated above, this single treatment of the board is necessitated by the irregularities or dimensional variations is the raw wood.
Another disadvantage with such single-board machines that are designed to run faster is accuracy. As the speed, or piece rate, is increased, accuracy is lost. Running single boards through the machine faster increases the number and ease of which boards are damaged. In addition, the precision of the cuts is lost, thus reducing the yield rate, and producing more defective lumber. Furthermore, initial costs are increase significantly, maintenance costs are increased, and safety decreases.
Therefore, the dual goals of increased yield rate and increased piece rate appear at times to be at odds; increased yield rate requiring accuracy and unique treatment of each board, and increased piece rate requiring speed and equal treatment of each board. The desire for efficient yield rates prevents boards from simply being processed together. Thus, conventional equipment has been designed to treat each board individually and one at a time to achieve an efficient yield, but to do so as rapidly as possible to satisfy a rapid piece rate.
Therefore, it would be advantageous to develop a method and apparatus to position, orient, and/or feed multiple boards to optimize the piece rate, while still optimizing the yield from each board. It would also be advantageous to develop a method and apparatus to more efficiently and rapidly process the boards to maximize both the production rate and the yield rate. It would also be advantageous to develop such a method and apparatus capable of improving the handling of the boards.